WO1991011502A1

WO1991011502A1 - Coal and oil upgrading by microagglomeration and thermopelletizing process ('comat' process)

Info

Publication number: WO1991011502A1
Application number: PCT/CA1991/000020
Authority: WO
Inventors: Jerzy Stefan Janiak
Original assignee: Alberta Research Council
Priority date: 1990-01-24
Filing date: 1991-01-21
Publication date: 1991-08-08
Also published as: CA2008470A1

Abstract

An improved solid fuel and improved liquid fuel are obtained from a feed coal and feed oil by a method which comprises the steps of: (a) forming microagglomerates of finely divided coal; (b) combining said microagglomerates generated from finely divided coal with up to 55 % by weight of dry coal of a low quality feed oil; (c) thermally treating the microagglomerates and feed oil mixture with a carrier gas at a temperature of between 350 °C and 420 °C at substantially atmospheric pressure to form a solid made of improved quality coal and a liquid made of improved quality oil; and (d) processing the improved quality coal thus formed to produce substantially uniform particles with improved strength.

Description

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Technical Field

The present invention relates to a method for producing an improved solid fuel and an improved liquid fuel from a feed coal and a feed oil by using a modified agglomeration process, a method for separating the feed coal from the feed oil, and a means for transforming the solid product obtained into particles of uniform size and shape and improved compressive strength.

Background Art

The process of oil agglomeration provides a method for removing impurities from coal by combining an aqueous slurry of finely divided coal particles with a bridging liquid. The bridging liquid many either be a heavy oil, a light oil, or a combination of both, depending upon the type of coal which is the subject of the agglomeration process. The combination of the bridging liquid with the carbonaceous constituents of the coal causes the mixture to agglomerate, due to the substantially hy rophobic nature of the coal particles. The size of the agglomerates increases as the mixture is agitated over a period of time. The agglomeration process is widely known and is described in U.S. Patent Nos. 4,209,301 and 4,153,419, and in Canadian Patent No. 1,216,551.

Once the agglomerates reach a desired size, they can be separated from the water and inorganic material remaining in the slurry by screening or other mechanical means. The agglomerates in turn can be treated to separate the bridging liquid from the coal particles. This process is described for various types of coals and bridging liquids in U.S. Patent No. 4.415.335 (Mainwaring et al) and U.S. Patent No. 4.854.940 (Janiak et al) .

One disadvantage of the above procedure is that it can take hours or even days to produce agglomerates of sufficient size such that recovery of the bridging liquid from the coal can be accomplished efficiently to produce a solid fuel of suitable stability and strength. While increasing the amount of bridging liquid that is used will accelerate the agglomeration process. the addition of bridging liquid past an optimum amount causes the agglomerates to become soft, distorted and may result in their sticking together to form a mushy lump. Attempts to recover the bridging liquid from such soft and distorted agglomerates without disintegrating the agglomerates have not been successful.

A further disadvantage of the above procedure is that it is directed solely at the upgrading of coal, and is not a practical means for the upgrading of the bridging liquid in significant quantities.

There is therefore a need for a process that can be used to simultaneously upgrade both coals and the bridging liquid quickly and efficiently so that the upgraded bridging liquid is produced in sufficient quantities to make the process commercially feasible for the upgrading of oils. Disclosure of Invention

It is thus an object of the present invention to provide a method for shortening the length of time required for the upgrading of coal using oil agglomeration techniques.

It is yet another object of the present invention to provide a commercially feasible method for the simultaneous upgrading of both coal and oil using oil agglomeration techniques.

It is yet another object of the present invention to provide a method for the production of particles of upgraded coal of uniform shape and dimensions with increased particle strength over that obtained by conventional agglomeration techniques.

These and other objects of the present invention will be apparent from the following description and appended claims.

The present invention provides a method for the simultaneous upgrading of coal and oil which according to one aspect, comprises the steps of forming microagglomerates of finely divided coal, combining microagglomerates generated from finely divided feed coal with up to 55% by weight of dry coal of a low quality feed oil. thermally treating the microagglomerates and feed oil mixture by contacting it with a carrier gas at a temperature of between 350°C and 420 c at substantially atmospheric pressure to form a solid made of improved quality coal and a liquid made of improved quality oil, and processing the improved quality coal to produce substantially uniform particles with improved strength. According to another aspect, a calcium compound is added to the microagglomerates along with the feed oil and according to yet another aspect, a binding agent is added to the improved quality coal prior to processing it. The feed coal may be bituminous, sub-bituminous or lignitic. The feed oil may be a light hydrocarbon, diesel oil, kerosene, naphtha, a heavy oil, bitumen, or mixtures thereof. The carrier gas may be any inert gas or may be steam. The processing of the improved quality coal may take place in an extruder, pellet mill or briquetting machine.

The binding agent which is added according to one aspect of the invention may be anthracene oil, pitch, bitumen, atactic polypropylene or any other substance commonly used as a binding agent.

Brief Description of Drawings

In the accompanying figures:

FIG 1 - is a schematic diagram of the steps involved in the present invention according to its various aspects.

FIG 2 - is a table showing the effect of change of temperature at which the thermal treatment step is performed upon the physical characteristics of the improved quality coal, where the feed coal is a - 5

subbituminous coal, the feed oil is a heavy oil with a specific gravity of API-12.2 (Lindberg oil) of which 50% by weight of dry feed coal is added to the microagglomerates, and the carrier gas is steam.

FIG 3 is a table showing the effect of change of temperature at which the thermal treatment step is performed upon the

10 recovery of oil from the improved quality coal. where the feed coal is a subbituminous coal. the feed oil is Lindberg oil of which 35% by weight of dry feed coal is added to the

15 microagglomerates. and the carrier gas is steam.

FIG 4 is a table showing the effect of change in the amount of feed oil added to the microagglomerates upon oil recovery at

20 410°C, where the feed coal is a subbituminous coal. the feed oil is Lindberg oil, and the carrier gas is steam.

FIG 5 is a table showing the effect of change

25 of temperature at which the thermal treatment step is performed upon the physical characteristics of the improved quality coal, where the feed coal is a subbituminous coal, the feed oil is

30 Lindberg oil of which 50% by weight of dry feed coal is added to the microagglomerates, and the carrier gas is steam.

FIG 6 - is a table showing properties of feed coal, feed agglomerates and the products obtained after thermal treatment, where the feed coal is a subbituminous coal, the feed oil is Lindberg oil of which 50% by weight of dry feed coal is added to the microagglomerates. and the carrier gas is steam.

Best Mode for Carrying Out Invention

Referring to Figure 1, the first step in the process of the present invention is the formation of microagglomerates of feed coal (10). The feed coal may be any type of coal which is sought to be upgraded, including both bituminous and subbituminous coals. There is no minimum size of microagglomerate which must be used. As a result. the duration of the agglomeration process may be greatly shortened, because there is no need to continue the process to permit the growth of the agglomerates. Where the feed coal contains a large amount of clay, the preferred process for agglomeration is that described in P.C.T. Application No. PCT/US89/03193 (Pawlak et al) filed July 27, 1989. and entitled "Process for Removing Pyritic Sulfur from Bituminous Coals". Where the feed coal has a low clay content, the preferred process for agglomeration is that described in Canadian Patent No. 1.216.551. The agglomeration process may be carried out in laboratory batch reactors, including either a stirred vessel or a Denver Standard Laboratory Flotation Machine.

The second step in the process is the addition and blending with the microagglomerates of the feed oil in quantities of up to 55% by dry weight of feed coal (12). The feed oil may be any type of oil which is sought to be upgraded, including light hydrocarbons, diesel oil, kerosene, naphtha, heavy oil, bitumen, or mixtures thereof. If it is necessary or desirable to reduce the emission of sulfur dioxide during combustion of the improved quality coal, calcium compounds in particles ranging in size from between 0.01 mm to 0.1 mm may be added during this step as well (14). Suitable calcium compounds include calcium carbonate, calcium nitrate, calcium acetate, calcium formate and like compounds. The mixing (16) of the feed oil and calcium compound may take place using any form of mixer or blender normally used in the food processing, pharmaceutical, or chemical industries.

The third step in the process is the upgrading of the feed coal and feed oil and the separation of the improved quality coal from the improved quality oil (18) by thermal treatment. This step involves contacting the mixture produced in the second step above with steam or an inert gas (20) at a temperature of between 350°C and 420°C at near atmospheric pressure. With the exception of the temperature at which this step is performed, this third step of the process is described fully in U.S. Patent No. 4,854,940 (Janiak et al) . The loss of volatile matter content when this step is performed at temperatures of greater than 350°C as reported in U.S. Patent No. 4.854.940 (Janiak et al) is not a disadvantage in the present invention, because the inherent compressive strength of the microagglomerates does not have to be relied upon as a source of strength for the improved quality coal. This third step produces the improved quality coal (24), improved quality oil (26). and a gaseous by-product or by-products (22). The improved quality oil may be recovered in the manner as disclosed in U.S. Patent No. 4.854,940 (Janiak et al), and the gaseous by-products may be recovered using any typical means for gas recovery.

The fourth step in the process is the transformation of the improved quality coal obtained in the third step above into a product consisting of uniform particles with improved strength (24). The improved quality coal is formed into either pellets or briquettes as required by using a typical extruder, pellet mill or briquetting machine. In order to achieve best results in the formation of the pellets or briquettes, the temperature of the improved quality coal following the third step and during the fourth step should be maintained at no less than 400°C. The binding of the particles of the improved quality coal during the pelletization or briquetting process is facilitated by the residual bridging liquid and feed oil contained in the improved quality coal. If there is an insufficient amount of residual bridging liquid and feed oil in the improved quality coal to facilitate optimum bonding of the improved quality coal particles during the pelletization or briquetting process, any of the binding agents commonly used in such processes such as anthracene oil, pitch, bitumen and atactic polypropylene, may be added.

The process of the present invention results in increased calorific value and mechanical strength and decreased moisture capacity of the improved quality coal compared with the feed coal, and a decrease in the sulfur content of the improved quality oil compared with the feed oil.

In Figures 2, 3 and 5, test results demonstrating the effect of the temperature at which the third step of the process is conducted upon the recovery of the products of the process are shown where the feed coal is a subbituminous coal, the feed oil is Lindberg oil of which 50% by weight of dry feed coal is added, and the carrier gas is steam. As may be seen from these Figures, recovery of the improved quality oil increases as the temperature at which the third step of the process is conducted increases. while the total recovery of combustible material decreases as the temperature at which the third step is conducted increases. Figure 4 demonstrates that the percentage of oil recovery during the third step increases as the percentage of feed oil relative to dry weight of feed coal increases from 16% to 50%, where the feed coal is a subbituminous coal, the feed oil is Lindberg oil. and the carrier gas is steam. Figure 6 shows test results demonstrating the physical properties of the improved quality coal following the third step being conducted at different temperatures, where the feed coal is a subbituminous coal, the feed oil is Lindberg oil of which 50% by dry weight of coal is added, and the carrier gas is steam.

The results presented in Figures 2„ 3, 4. 5. and 6 reveal that recovery of oil increased as the temperature at which the third step was conducted increased to 410 C, while the highest calorific value obtained for the improved quality coal occurred when the third step was conducted at a temperature of

350 C.

Claims

1. A method for the upgrading of coal and oil, comprising the steps of:

(a) forming microagglomerates of finely divided coal;

(b) combining said microagglomerates generated from finely divided coal with up to 55% by weight of dry coal of a low quality feed oil;

(c) thermally treating the microagglomerates and feed oil mixϊύre by contacting it with a carrier gas at a temperature of between 350°C and ^* 420°C at substantially atmospheric pressure to form a solid made of improved quality coal and a liquid made of improved quality oil; and

(d) processing the improved quality coal thus formed to produce substantially uniform particles with improved strength.

2. A method according to claim 1 further comprising the step of adding a calcium compound to the microagglomerates along with the feed oil.

3. A method according to claim 1 further comprising the step of adding a binding agent to the improved quality coal prior to processing step (d).

4. A method according to claim 1. 2 or 3 wherein the coal which is used is a subbituminous coal.

5. A method according to claim 1, 2 or 3 where in the feed oil is a heavy oil having a specific gravity in the range 10-20° API.

6. A method according to claim 1. 2 or 3 wherein the carrier gas used is steam.

7. A method according to claim 1. 2 or 3 wherein the processing of the improved quality coal takes place in an electrically driven pellet mill.

8. A method according to claim 1. 2 or 3 wherein the upgrading of the coal and the oil takes place simultaneously.

9. A method according to claim 3 wherein the binding agent comprises the residual quality coal.